Here's a quick test of the new Popular Mechanics boiler running a Westinghouse type twin, and showing the release valve blow off. The valve pops twice, a little below 20 lbs because of boiling pressure peaks in the copper coil below, but opens steadily at 20 psi. Unfortunately you can't read the gauge easily since it's out of focus -- the second marking is 20 lbs.

ps because of the frame rate of the video it strobes the engine rotation and it looks very slow. The sound gives you a better idea of the actual speed -- about 750 RPM I think.

These details make it seem difficult to me to build. I have no idea where I'd find bronze balls or wire, or how I would drill and tap the ball, and I don't like the idea of the spring being in the boiler as much as outside. Nevertheless I'm sure these give satisfaction -- just not what I'm favoring right now.

I know this is an old post, but since I missed it the first time around, I thought I should take the opportunity to chime in now.

First, brilliant build. Thanks for sharing.

Nowadays it seems that just about every podunk town has a piercing/tattoo parlor on every corner. Those places will sell piercing jewelry consisting of a couple of steel or titanium balls, threaded to accept a post. Sizes range from 3mm to 8mm diameter ball and with a post length of up to ~24mm. This jewelry is available for somewhere in the €5.00 range.

You can use the threaded balls and posts in valves, governors, or put 'em in your

I've never had a tattoo, basically because I'm torn between that and accupuncture and can't make up my mind about it. So josh you're saying I ought to visit one of these places and ask to look at their titanium ..... uhhhh .....spheroids?

Well seriously, that might work for one of the Tubal Cain type small safety valves, if of the right size.

While I'm sure it's sufficient, I don't like his design as much though, because the spring (and stem) is on the boiler side of the valve, instead of the outside.

In the external spring type, the steam has a clear passage through the valve orifice and seat, the parts count is lower, the ball can rotate to even out wear, and the spring compression (and steam pressure) are somewhat adjustable, and the spring can be replaced and inspected without removing the saftety valve body from the boiler.

I suppose you could use a stem and ball running the stem and spring externally, I'm not sure what the stem would do unless you had a guide bore for the stem before the spring, and that could jam with debris.

Personally, I think a simple floating ball and external spring, is not only the easiest to build, but probably the most reliable for this small size and type of boiler. That's just my opinion.

ps. I think a proper seat for the ball is important to avoid leaks. The seat should be convex conical -- like a volcano in shape. It's true that to finally finish the seat writers generally call for tapping a ball lightly on the seat to form a very slight impression, but it may not work as well on a simple flat seat in this size valve.

You can make a cutter to from the seat easily on the lathe in drill rod/silver steel and harden and temper ( or not probably if just cutting a seat or two in brass).

Well, now that you've got me thinking about it, I just thought of one advantage of the internal spring and stem type. It's relatively tamper proof.

To alter it you'd have to remove the valve body and change the spring and retainer on the stem. Many of these small boilers were intended as toys, and a tamper proof safety valve is pretty desirable in that case.

The worst for tampering, is the external weighted type, like the original PM Boiler. Kids could add weight. But of course, it didn't even work as drawn.

Nowadays it seems that just about every podunk town has a piercing/tattoo parlor on every corner. Those places will sell piercing jewelry consisting of a couple of steel or titanium balls, threaded to accept a post. Sizes range from 3mm to 8mm diameter ball and with a post length of up to ~24mm. This jewelry is available for somewhere in the €5.00 range.

You can use the threaded balls and posts in valves, governors, or put 'em in your

Just a thought.

Josh, thank you for that.

I have a few microscope attachments with broken operating levers. The levers comprise a thin stem with a tapped (about 10 BA) ball (about ⅛" diameter) on the end. OK, I OUGHT to be able to make replacements but parts that small are a bit fiddly and time is short. Maybe you've just alerted me to a workaround.

Hey! Where did that 'spell Check' button come from? I've never noticed it before!!!!

Logged

Best regards,

Pete W.

If you can keep your head when all about you are losing theirs, you haven't seen the latest change-note!